A cleanroom is an environment, typically used in manufacturing or scientific research, that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. A cleanroom has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size. To give perspective, the ambient air outside in a typical urban environment contains 35,000,000 particles per cubic meter in the size range 0.5 μm and larger in diameter, corresponding to an ISO 9 cleanroom, while an ISO 1 cleanroom allows no particles in that size range and only 12 particles per cubic meter of 0.3 μm and smaller.
Cleanrooms can be very large. Entire manufacturing facilities can be contained within a cleanroom with factory floors covering thousands of square meters. They are used extensively in semiconductor manufacturing, biotechnology, the life sciences and other fields that are very sensitive to environmental contamination.
The air entering a cleanroom from outside is filtered to exclude dust, and the air inside is constantly recirculated through high-efficiency particulate air (HEPA) and/or ultra-low penetration air (ULPA) filters to remove internally generated contaminants. Staff enter and leave through airlocks (sometimes including an air shower stage), and wear protective clothing such as hoods, face masks, gloves, boots and coveralls. Equipment inside the cleanroom is designed to generate minimal air contamination. Only special mops and buckets are used. Cleanroom furniture is designed to produce a minimum of particles and to be easy to clean. Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded, and alternatives used. Some cleanrooms are kept at a positive pressure so that if there are any leaks, air leaks out of the chamber instead of unfiltered air coming in. Some cleanroom HVAC systems control the humidity to low levels, such that extra equipment is necessary (e.g., “ionizers”) to prevent electrostatic discharge (ESD) problems.
Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent airflow principles. Laminar, or unidirectional, air flow systems direct filtered air downward in a constant stream towards filters located on walls near the cleanroom floor or through raised perforated floor panels to be recirculated. Laminar airflow systems are typically employed across about 80 percent of a cleanroom ceiling to maintain constant air processing. Stainless steel or other non-shed materials are used to construct laminar airflow filters and hoods to prevent excess particles entering the air. Turbulent, or non-unidirectional, airflow uses both laminar airflow hoods and non-specific velocity filters to keep air in a cleanroom in constant motion, although not all in the same direction. The rough air seeks to trap particles that may be in the air and drive them towards the floor, where they enter filters and leave the cleanroom environment.
In the pharmaceutical industry, the term “isolator” covers a variety of pieces of equipment. One group has the main objective of providing containment for the handling of dangerous materials either aseptically or not. Another group has the main objective of providing a microbiologically controlled environment within which aseptic operations can be carried out. Containment isolators often employ negative internal air pressure and most isolators used for aseptic processing employ positive pressure. A sporicidal process, usually delivered by gassing, can be used to aid microbiological control. Some large-scale isolators provide an opening, often called a mouse hole, to permit continuous removal of sealed product. Other isolators remain sealed throughout production operations.
Aseptic operations can include sterility testing or aseptic processing to produce medicinal products. Isolators are used to provide a microbiologically controlled environment for aseptic processing for producing medicinal products labeled as sterile. Isolators could be seen as a more encompassing development of the barriers used in conventional clean rooms. The clean room barriers evolved from plastic flexible curtains through to rigid barriers with glove ports. The objectives of barriers are to increasingly separate the surrounding clean room including the operator from the critical zone where aseptic operations are carried out and sterile materials are exposed. When the degree of containment is nearly complete, sporicidal procedures can be applied without harming the operators. Accordingly, an isolator is an arrangement of physical barriers that are integrated to the extent that the isolator can be sealed in order to carry out a routine leak test based on pressure to meet specified limits. Internally it provides a workspace, which is separated from the surrounding environment. Manipulations can be carried out within the space from the outside without compromising its integrity. Industrial isolators used for aseptic processing are isolators in which the internal space and exposed surfaces are microbiologically controlled. Control is achieved by the use of microbiologically retentive filters, sterilization processes, sporicidal processes (such as by gassing) and prevention of recontamination from the external environment. A sporicidal process is a gaseous, vapor or liquid treatment applied to surfaces, using an agent that is recognized as capable of killing bacterial and fungal spores. The process is applied to internal surfaces of the isolator and external surfaces of materials inside the isolator, when conventional sterilization methods are not required.
Cleanrooms are classified according to the number and size of particles permitted per volume of air. Large numbers like “class 100” or “class 1000” refer to FED-STD-209E, and denote the number of particles of size 0.5 μm or larger permitted per cubic foot of air. The standard also allows interpolation, so it is possible to describe, for example, “class 2000”. Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 μm or larger permitted per cubic meter of air. For example, an ISO class 5 cleanroom has at most 105=100,000 particles per cubic meter. Because 1 m3 is approximately 35 ft3, the two standards are mostly equivalent when measuring 0.5 μm particles, although the testing standards differ. Ordinary room air is approximately class 1,000,000 or ISO 9. A discrete-particle-counting, light-scattering instrument is used to determine the concentration of airborne particles, equal to and larger than the specified sizes, at designated sampling locations.
US FED STD 209E Cleanroom Standardsmaximum particles/ft3ISOClass≧0.1 μm≧0.2 μm≧0.3 μm≧0.5 μm≧5 μmequivalent1357.5310.007ISO 3103507530100.07ISO 41003,5007503001000.7ISO 51,00035,0007,50030001,0007ISO 610,000350,00075,00030,00010,00070ISO 7100,0003.5 × 106750,000300,000100,000700ISO 8
ISO 14644-1 Cleanroom Standardsmaximum particles/m3FED STD 209EClass≧0.1 μm≧0.2 μm≧0.3 μm≧0.5 μm≧1 μm≧5 μmequivalentISO 1102.371.020.350.0830.0029ISO 210023.710.23.50.830.029ISO 31,000237102358.30.29Class 1ISO 410,0002,3701,020352832.9Class 10ISO 5100,00023,70010,2003,52083229Class 100ISO 61.0 × 106237,000102,00035,2008,320293Class 1,000ISO 71.0 × 1072.37 × 1061,020,000352,00083,2002,930Class 10,000ISO 81.0 × 1082.37 × 1071.02 × 1073,520,000832,00029,300Class 100,000ISO 91.0 × 1092.37 × 1081.02 × 10835,200,0008,320,000293,000Room air
Both FS 209E and ISO 14644-1 assume log-log relationships between particle size and particle concentration. For that reason, zero particle concentration does not exist. The table locations without entries are non-applicable combinations of particle sizes and cleanliness classes, and should not be read as zero.
BS 5295 Cleanroom Standardsmaximum particles/m3Class≧0.5 μm≧1 μm≧5 μm≧10 μm≧25 μmClass 13,000000Class 2300,0002,00030Class 31,000,00020,0004,000300Class 4200,00040,0004,000
BS 5295 Class 1 also requires that the greatest particle present in any sample does not exceed 5 μm.
GMP EU Classificationmaximum particles/m3At RestAt RestIn OperationIn OperationClass0.5 μm5 μm0.5 μm5 μmClass A3,520203,50020Class B3,52029352,0002,900Class C352,0002,9003,520,00029,000Class D3,520,00029,000n/an/a
The term “sterility assurance level” (SAL) is used in microbiology to describe the probability of a single unit being non-sterile after it has been subjected to a sterilization process. For example, medical device manufacturers design their sterilization processes for an extremely low SAL—“one in a million” devices should be nonsterile. SAL is also used to describe the killing efficacy of a sterilization process, where a very effective sterilization process has a very low SAL.
In microbiology, it is considered impossible to prove that all organisms have been destroyed because: 1) they could be present but undetectable simply because they are not being incubated in their preferred environment, and 2) they could be present but undetectable because their existence has never been discovered. Therefore, SALs are used to describe the probability that a given sterilization process has not destroyed all of the microorganisms.
Mathematically, SALs referring to probability are usually very small numbers and so are properly expressed as negative exponents (e.g., “The SAL of this process is 10 to the minus six”). SALs referring to sterilization efficacy are usually much larger numbers and so are properly expressed as positive exponents (e.g., “The SAL of this process is 10 to the six”). In this usage, the negative effect of the process is sometimes inferred by using the word “reduction” (e.g., “This process gives a six-log reduction”).
SALs can be used to describe the microbial population that was destroyed by a sterilization process. Each log reduction (10−1) represents a 90% reduction in microbial population. So a process shown to achieve a “6-log reduction” (10−6) will reduce a population from a million organisms (106) to very close to zero.
In order to sterile or aseptically fill substances into containers or devices, such as pharmaceuticals, vaccines, and food products, cleanrooms and isolators have been employed in order to ensure the requisite SALs to maintain the filled product aseptic or sterile. However, as summarized above, cleanrooms and isolators can require substantial capital expenditures, operational costs, numerous controls, sophisticated and expensive facilities, and/or highly trained personnel. Accordingly, it would be desirable to sterile or aseptically fill substances without such cleanrooms and/or isolators, while nevertheless ensuring the requisite SALs to maintain the filled substances aseptic or sterile.
It is therefore an object of the present invention to overcome one or more of the above-described drawbacks and/or disadvantages of the prior art.